Production of saturated fatty acids



W wa-m United States Patent PRODUCTION OF SATURATED FATTY ACIDS Joseph N. Opie, ll/Iinneapolis, Minn., assignor to General Mills, Inc., a corporation of Delaware No Drawing. Application July 12, 1951, Serial No. 236,473

7 Claims. Cl. 260409) The present invention relates to a process of producing saturated fatty acids of good color from unsaturated fatty acids or mixtures of unsaturated fatty acids and saturated acids.

Saturated higher fatty acids, especially stearic acid and palmitic acid, are produced in a number of ways. Typical of these methods are pressing operations and solvent crystallization. In order to produce high quality saturated fatty acids by pressing, it is necessary to repeat the operation two or three times. High quality saturated fatty acids can be produced by solvent crystallization, but this necessitates the employment of expensive equipment, and moreover, the operation of such a process is. costly.

Attempts have been made to produce saturated fatty acids from unsaturated fatty acids by hydrogenation. However, difficulty has been experienced in attempting to get the color of such hydrogenated products sufficiently good to make them competitive with such products as crystallized stearic acid or triple-pressed stearic acid. In the hydrogenation process it is frequently necessary to subject the fatty acids to two distillations following hydrogenation and also it is frequently necessary to employ a bleaching operation following the distillation. These supplemental treatments are costly and furthermore tie up equipment which is ordinarily needed for other operations.

It has now been found that these difficulties with the prior methods of producing saturated fatty acids from unsaturated acids by hydrogenation can be avoided by conducting the hydrogenation in the presence of a bleaching earth which is added with the catalyst. It has been found that the bleaching earth very materially speeds up the hydrogenation process and, what is more important, the product obtained by distilling the hydrogenated product is found to be lighter in color and to have good color stability.

It is therefore an object of the present invention to provide a novel process of producing saturated fatty acids fiom unsaturated fatty acids by hydrogenation in the presence of a bleaching earth.

The invention is applicable. to a wide variety of fatty acid materials. Thus saturated fatty acids can be produced from unsaturated fatty acids or mixtures of unsaturated and saturated fatty acids. In general, it is desirable to produce saturated fatty acids having an iodine number of or less. Accordingly the starting material may have an iodine value of from 10 to 150 or more depending upon the available materials. Thus the mixed fatty acids from a fat or oil may be employed as a starting material, or, as is usually the case, some selected fraction thereof. In normal fatty acid operations it is customary to subject mixed fatty acids to some fractionation procedure, for example, by distillation, and to separate the predominantly saturated fatty acid fractions from the predominantly unsaturated fatty acid fractions. Normally the saturated fatty acid fractions which, of course, contain some unsaturated fatty acids, would be used as. a starting material for the present invention. Typical of these fractions 2,715,641 Patented Aug. 16, 1955 ice are saturated fractions frequently having iodine values Within the range of 30 to 65. Such mixtures are usually composed of palmitic, oleic, and linoleic acids with smaller quantities of stearic acid.

The fatty acid employed for the present process should be preliminarily treated to render it suitable for the process. Thus if the fatty acid feed is derived by splitting a good quality fat or oil, the split acids may be employed directly as feed stock for the hydrogenation process Without any further purification. However, if the fatty acids are obtained, for example, by acidulating soap stock, it will usually be found necessary to distill the acidulated soap stock to obtain a reasonably clean cut for the production of high quality saturated fatty acids. In other Words, the fatty acid feed stock should be preliminarily treated, depending upon its origin, in such a manner as to provide a reasonably light colored and clear feed stock.

A wide variety of bleaching earths may be employed during the hydrogenation. As the name bleaching earths indicates, these materials have some color removing properties, and in this way they are distinguished from the inert catalyst carriers or supports which have on occasion been used in hydrogenation. Any of the bleaching earths are effective for the purposes of the present invention, whereas inert materials such as diatomaceous earth, and the like, have been found to be ineffective. The bleaching earth is employed in a quantity of from 1% to 3% by weight based on the weight of the fatty acids being hydrogenated. Preferably the bleaching earth is employed in the amount of 2%.

Any of the usual nickel hydrogenation catalysts may be employed, such as Raney nickel and the reduced nickel catalysts, as, for example, reduced nickel formate or carbonate. Preferably they are employed in a quantity of about /z% nickel based on the weight of the fatty acid. Catalysts which have been particularly desirable have been metallic nickel catalysts in a hydrogenated oil carner.

The process may be carried out in the usual way in which hydrogenations are carried out. The feed stock and hydrogenation catalyst and bleaching earth are added to the hydrogenation vessel, and the vessel subjected to the temperature and hydrogen pressure conditions customary in hydrogenation. Typical of these conditions are 200 pounds per square inch of hydrogen at a temperature of 200 C. It will be apparent that other pressure conditions up to 1,000 pounds per square inch and higher may be employed.

In the examples described hereinafter, the hydrogenation was carried out as follows: The hydrogenations were run in a rocking bomb at 200 pounds per square inch maximum pressure and at a temperature of 200 C, The bomb Wascharged with the unsaturated fatty acid feed stock. The catalyst and bleaching earth were added and the bomb was closed and flushed with hydrogen. Pressure within the apparatus was then raised to 200 pounds per square inch by introducing hydrogen at this pressure. Heating was started and the hydrogenation was noted to begin at a temperature of 140 C. At this point the pressure had risen to approximately 220 pounds per square inch. As hydrogenation took place the pressure dropped and more hydrogen was introduced when the pressure dropped below pounds per square inch. Hydrogenation was considered to be complete when no pressure drop was noted when the system was at 200 pounds per square inch. The temperature was maintained at approximately 200 C. and did not exceed 210 C. When the reaction was complete the bomb was allowed to cool to less than 100 C., at which point it was opened and the catalyst and bleaching clay filtered from the product. The product was then distilled. As will be seen from the following examples, maximum color improvement and color stability jected to a bleaching operation.

Example 1 A distilled mixture of unsaturated higher fatty acids having an iodine number of 34.8 and an acid number of 215.3 was employed; 250 g. of these mixed fatty acids, 1.5g. of 24.2% nickel catalyst (Harshaw Reduced Nickel) and g. of a montmorillonite bleaching earth )Pikes Peak Clay No. 9077) were combined and placed in the hydrogenation bomb. The hydrogenation was carried out as described above and the product was vacuum distilled through an alembic still. A portion of the distilled product was bleached with 2% by weight of a bleaching earth (Super Filtrol F0). The distilled product had an acid number of 216.4 and an iodine number of 0.18. The productwas tested by determining the average light transmittances of the sample at 400, 425, 450, 475 and 500 Ratings were taken with a Coleman J r. Spectrophotometer and compared'with distilled'water rated at 100. The

purified product showed the following light transmittances:

Im'ti 1 3: or a a er Pmduct Color Heat testing Hydrogenated and distilled 95 86 Hydrogenated, distilled and bleached 98 87 'The heat testing referred to in. the above table is an accelerated aging test and involves heating a sample ina Nessler tube at 205 C. for 2 hours.

For comparative purposes an identical experiment was carried out in the absence of the bleaching earth. The following properties were noted in the product: acid number 214.3; iodine value 0.88. The product had the following light transmittance values:

' Init' l 32 18 a 81' Product Color Heat testing Distilled product 71 45 Distilled and bleached 89 59 Example 2 tance values:

but 1 3: or re a er Product Color Heat testing 7 Distilled product 71 52 Distilled and bleached 80 51 The preceding experiment was carried out in the same manner, but without the addition of the clay. After hydrogenation the product was distilled and had an acid number of 205.1 and an iodine value of 9.15. It had the following light transmittance values:

Int 1 it 1 1a a er Product Color Heat testing Distilled product 63 50 Distilled and bleached- 68 41 The product was 7 Example 3 A series of hydrogenations were carried out to compare the efiect of various bleaching earths on the reaction, and to compare the results obtained without the use of the bleaching earth. In all ofthese experiments undistilled mixed higher fatty acids having an acid number of 207.1 and an iodine number of 47.1 were employed. The hydrogenation was carried out at 200 pounds pressure at 200 C. and in the presence of 0.6% nickel based on the weight of the fatty acid. After hydrogenation each of the products was distilled and then bleached. The color transmittance values are shown in the following table:.

Color Clay Distilled Distilled and bleached After Heat Alter Heat llmtial Test Initial V 7 Test Montmorillonite:

acco 68 44 78 52 Palex 1H, pH

8.0-8.3 70 45 77 56 Palex 1, pH 4.0

4.2 67 44 76 48 Palex 11, pH 7.0-

Do 71 52 8O 51 Fuller's Earth:

Example 4 200 grams of acids resulting from the splitting of tallow were hydrogenated with 1.2% of Drew nickel catalyst. The hydrogenated product after distillation had an iodine value of 8.5. The light transmittance values for the prodnot are as follows:

I Inn" 1 ii l3, 8 er Product Color Heat testing Distilled product r e 63 32 Distilled and bleached 78 52 The same experiment was carried out using the same reactants in the same proportions, but in addition 2% of the clay of Example 1 was employed. The hydrogenated distilled product had an iodine value of 5.22. The light transmittance values for the product were as follows:

nun 1 iii 8 a 91 Product Color Heat testing Distilled product 73 49 Distilled and bleached 87 61 Example 5 in the presence of 0.6% of Drew nickel catalyst and in the presence of 2% of the same clay used for bleaching. Following the hydrogenation the product was distilled and the distilled productwas bleached with the same clay. For comparison purposes a series of similar experiments were run which differed in the following respects. In one experiment the pre-bleaching was omitted and no clay was employed during the hydrogenation; in another only the pre-bleaching was omitted; in a third only the clay 6 bleaching earth, until the iodine value of the fatty acids is reduced to about 5, and thereafter distilling and bleaching the hydrogenated fatty acids.

5. Process of producing higher saturated fatty acids of during the hydrogenation was omitted. Each of these improved color, which comprises hydrogenating an unproduct was tested for light transmittance and the values saturated fatty acid with a nickel hydrogenation catalyst obtained are shown in the following table: in the presence of a montmorillonite clay until the fatty Color Pretreatment Hydrogegfiggn Treat- Distilled Prod. Dist. Bleached Prod.

Aiter Heat After Heat Initial Test Initial Test None H: in presence of 81 62 89 66 Drew nickel catalyst. Do Hzinpresence of Drew 80 62 91 74 ndigkel catalyst+2% y. Prebleachwith2% clay" Hginpresence of Drew 77 60 86 69 nickel catalyst. Do Hainpresence ofDrew 84 65 93 79 migkel catalyst+2% c y.

I claim as my invention:

1. Process of producing saturated higher fatty acids of good color, which comprises hydrogenating an unsaturated higher fatty acid in the presence of a nickel hydrogenation catalyst, and in the presence of a bleaching earth to reduce the iodine value of the fatty acids below about 5, and subsequently distilling the hydrogenated fatty acids.

2. Process of producing saturated higher fatty acids of good color, which comprises hydrogenating an unsaturated higher fatty acid in the presence of a nickel hydrogenation catalyst, and in the presence of a bleaching earth to reduce the iodine value of the fatty acids below about 5, and subsequently distilling and bleaching the hydrogenated fatty acids.

3. Process of producing higher saturated fatty acids of good color, which comprises hydrogenating a mixture of higher fatty acids having an iodine value within the approximate range of 30 to 65 with a nickel hydrogenation catalyst in the presence of from 1% to 3% of a bleaching earth, until the iodine value of the fatty acids is reduced to about 5, and thereafter distilling the hydrogenated fatty acids.

4. Process of producing higher saturated fatty acids of good color, which comprises hydrogenating a mixture of higher fatty acids having an iodine value within the approximate range of 30 to 65 with a nickel hydrogenation catalyst in the presence of from 1% to 3% of a acid has an iodine value of about 5, and thereafter distilling the hydrogenated fatty acids.

6. Process of producing higher saturated fatty acids of improved color, which comprises selecting a distilled fraction of the fatty acids of an oil, said fraction having an iodine value within the approximate range of 30 to 65, subjecting said fraction to hydrogenation in the presence of a nickel hydrogenation catalyst and in the presence of a bleaching earth until the fatty acids have an iodine value of about 5, and thereafter distilling the hydrogenated product.

7. Process of producing higher saturated fatty acids of improved color, which comprises selecting a distilled fraction of the fatty acids of an oil, said fraction having an iodine value Within the approximate range of 30 to 65, subjecting said fraction to hydrogenation in the presence of a nickel hydrogenation catalyst and in the presence of a bleaching earth until the fatty acids have an iodine value of about 5, and thereafter distilling and bleaching the hydrogenated product.

References Cited in the file of this patent UNITED STATES PATENTS 

1. PROCESS OF PRODUCING SATURATED HIGHER FATTY ACIDS OF GOOD COLOR, WHICH COMPRISES HYDROGENATING AN UNSATURATED HIGHER FATTY ACID IN THE PRESENCE OF A NICKEL HYDROGENATION CATALYST, AND IN THE PRESENCE OF A BLEACHING EARTH TO REDUCE THE IODINE VALUE OF THE FATTY ACIDS BELOW ABOUT 5, AND SUBSEQUENTLY DISTILLING THE HYDROGENATED FATTY ACIDS. 